From: Mauro Carvalho Chehab
Sent: 21 June 2021 14:40
As warned by smatch: drivers/media/usb/uvc/uvc_v4l2.c:911 uvc_ioctl_g_input() error: doing dma on the stack (&i) drivers/media/usb/uvc/uvc_v4l2.c:943 uvc_ioctl_s_input() error: doing dma on the stack (&i)
those two functions call uvc_query_ctrl passing a pointer to a data at the DMA stack. those are used to send URBs via usb_control_msg(). Using DMA stack is not supported and should not work anymore on modern Linux versions.
So, use a kmalloc'ed buffer.
...
- buf = kmalloc(1, GFP_KERNEL);
- if (!buf)
return -ENOMEM;- ret = uvc_query_ctrl(chain->dev, UVC_GET_CUR, chain->selector->id, chain->dev->intfnum, UVC_SU_INPUT_SELECT_CONTROL,
&i, 1);
buf, 1);
Thought...
Is kmalloc(1, GFP_KERNEL) guaranteed to return a pointer into a cache line that will not be accessed by any other code? (This is slightly weaker than requiring a cache-line aligned pointer - but very similar.)
Without that guarantee you can't use the returned buffer for read dma unless the memory accesses are coherent.
David
- Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)